Good nails are to be had any were; if a body’s willing to do the leg work. These “good” nails are ones vindictive of the old ones, they’re cut and made of iron.
Finding these modern nails one must first look to the masonry arts; these nails are cut fine, but hardened and herein lies the problem.
These modern hardened nails are a bear to work with if the user is slightly unsure of the use of cut nails, they feel like the hammer is hitting a wall made of solid Sioux Quartzite; they also have a larger point than the old boys which can cause havoc in selecting a pilot hole size and it will split the stock much easily. The solutions thus presents themselves by trial and error. The first is finding the right pilot hole size: this varies from nail to nail, but the simplest solution is to take the nail and gauge were the middle to three-quarters of the shaft is and that thickness is the thickness of pilot bit should be. The next solution is look at the grain of the stock at hand, then look at the head of the nail, this head makes a rectangle, position the rectangle so that it runs parallel to the grain. With these two solutions most would contend that there is no more to be fixed, yet there is the problem that these little buggers are damn hard to pound. The solution is to grind a point on then. These masonry nails are tough, as they should be, but the industrious mechanic will take the nail to the coarse grind stone and grind a point on the little beauties thus making the driving of these modern nails much easier on the carpenter, their tools and the stock.
With all this in mind go and find a local antique store, flea market, or reclaimed wood store and ask; one will be surprised at the wealth of information received if one is polite.